Flipkart — Buy back

I've purchased mobile phone on 23Jan 2021 with buy back guarantee policy, so according to that from 31st March 21 to 29 Jan 21 i'm eligible to upgrade to a new phone with a value of rs 25200 by returning my old phone, so now I am trying in sep 21, i could not avail it as it gives out error on both desktop and mobile platform saying abb is not enabled for your account / imei / warranty details as undefined,

Nearly 10-15 conversations have been done so far over phone call they have promised me twice that issue will be resolved within few hours and this might be happened bcoz of technical glitch, but still I m facing issue